Functions of the various microtubular systems that have been described in many different cells are mostly unknown. The principal investigator is familiar with the fine structure of a number of these structures in ciliated protozoa. Within Paramecium caudatum is a system which has a location and association with other cytoplasmic components which suggests an involvement in intracellular movement of particles. These bands of microtubules arise near the mouth region. Disc-shaped vesicles are found lined up along these bands in ways which suggest that they are associated with and move along the microtubules. Freeze-etch and serial sectioning techniques will be used to describe this system in detail. Cytochemical markers, autoradiography and antimitotic agents will be used in an attempt to show evidence for the site of origin of these vesicles, the patterns of movement of the vesicles, and the role of the vesicles in the cell. Cell fragmentation and negative staining will provide some clue to the firmness of attachment of these discs to the microtubules. The fine structure of selected deep sea eucaryotes will also be studied to see if the high pressures in which these cells live has resulted in any changes in their morphology. Special attention will be given to a search for microtubules since these have been found to be disassembled at high hydrostatic pressure. The specimens will be fixed while still at the depths at which they are collected to prevent artifacts as a result of subjecting the cells to reduced pressure.